I am sure that it holds for ordered sets but in the case of unordered set such as $$A={(1,2,3)}, B={(5,1,4)}$$ it does not hold.
As $A+B$ will be ${(6,3,7)}$.
$\inf(A+B)=3$ $$\inf(A)+\inf(B)=1+1=2$$
I am sure that it holds for ordered sets but in the case of unordered set such as $$A={(1,2,3)}, B={(5,1,4)}$$ it does not hold.
As $A+B$ will be ${(6,3,7)}$.
$\inf(A+B)=3$ $$\inf(A)+\inf(B)=1+1=2$$